EAS systems are well known for the prevention or deterrence of unauthorized removal of articles from a controlled area. In a typical EAS system, security tags are attached to articles to be protected. The security tags are designed to interact with an electromagnetic field located at the exits of the controlled area. If a security tag is brought into the electromagnetic field or “interrogation zone”, the presence of the security tag is detected and appropriate action is taken. For a controlled area such as a retail store, the appropriate action taken for detection of a security tag may be the generation of an alarm. Some types of security tags remain attached to the articles to be protected, but are deactivated prior to authorized removal from the controlled area by a deactivation device that changes the characteristics of the security tag so that the security tag will no longer be detectable in the interrogation zone.
In some scenarios, the deactivation device includes a handheld deactivation device for use by store employees. The handheld deactivation device may be part of a handheld bar-code scanner or other battery powered device. In this case, power needs to be used very efficiently in order for the battery's charge to last for several hours. Conventionally, a relatively large amount of battery power has been wasted since the transmit current (or power) of the deactivator is fixed to a selected level.